Hepatitis C virus (HCV) infection causes acute and chronic hepatitis, liver steatosis, cirrhosis, and eventually hepatocellular carcinoma (HCC). The molecular events of HCV infection leading to HCC formation are still poorly understood. HCV core protein has been proposed to be one of the key viral components contributing to oxidative stress, steatosis, and carcinogenesis. In this regard, we have established a human hepatoma cell model of transient and efficient HCV core protein expression. Cells expressing core protein, especially of the lb genotype, displayed increased proliferation and cell cycle progression. Microarray analysis revealed upregulation of genes involved in cell growth and oncogenic signaling pathways in response to core protein expression. Of particular interest is the up-regulation of both wnt-1 and its downstream target WISP-2. These observations suggest that wnt-1 signaling pathway may be activated by HCV core protein and partly mediate cell proliferation induced by the core protein. The wnt-1 signaling pathway is known to play an important role in cell growth and tumorogenesis. The disregulation of wnt-1 pathway has been found in many human tumors including liver cancer. Therefore, further characterization of wnt-1/WISP-2 signaling in HCV core expressing cells and its effect on regulation of liver cell growth may probe into the mechanisms by which the core protein induced cell proliferation. Specific Aim 1 will determine the structural-functional basis whereby the core protein stimulates cell proliferation. The responsible sequence will be defined by deletion mutants, and genotype specific determinant(s) will be located via chimeric constructs. Specific Aim 2 will examine the role of wnt-1/WISP-2 signaling pathway in mediating enhanced cell proliferation. We will further validate activation of the wnt-1/beta-catenin pathway is indeed activated by HCV core protein and examine whether inhibition of wnt-1/WISP-2 protein expression will block cell growth as elicited by core protein. These studies may elucidate molecular mechanisms of core induced cell proliferation and provide novel targets for prevention of HCV induced liver cancer.